LEDs are basically current devices that have a voltage drop across them. They will have a maximum current they can handle before they burn up. Limiting the current in one way or another to less than their maximum current rating will allow them to survive a LONG time. This is what MrForbes is doing with the resistor in series with their LED and voltage regulator (LM7805).
This year we decided to add a "Photon Cannon" to our robot to aid the driver in shot alignment.
To do this, we chose to use a
constant current source LED driver and a
3W LED.
Using the constant current source sets the current through the LED to either 330mA or 660mA, depending on how we configure the board, regardless of the battery voltage. This way it does not dim or flicker as we drive or manipulate things. We mounted a single lens 10cm (focal length of the lens) in front of the LED to give us a nicely collimated beam. The intensity of this beam is such that we decided not to leave the photon cannon on all the time, but switch it on only when needed. This is achieved by using a Spike relay.
Let's just say, it works REALLY well.
BTW, the LEDs we are using are are also available in
Red,
Green, and
Blue. All of these work well and look really great!